The highend fullsize headphones need better desktop DAC, AMPs help to show there best and they are supperior sounding but only with whole better setup. Custom highend IEMs and universal highend IEMs also improve more with AMPs, DAC help but they sound great out of any DAPs. So for portable, home use the IEMs are better pick with or without AMPs and DAC, for home use fullsize headphones are better if built whole destop rig.